- Enzymes speed up reactions in the body and are therefore called biological catalysts.
- They catalyse chemical reactions occuring in respiration, photosynthesis and protein synthesis of living cells.
- The substrate molecule fits into the active site of the enzymes like a key a lock
- 'Lock and key mechanism'
- It also explains why each enzyme can only work on a particular substrate. Specificty and it happens becuase the substrate has to be the right shape.
- Enzymes all work best at a particular temperature and pH. This is called the optimum. Any change from the optimum will slow down the reaction.
- Enzyme activity is affected by pH and temperature:
- At low temperatures molecules are moving slowly so the substrate and enzyme are less likely to collide.
- At very high/low pH values and high temps the enzymes active site changes shape. This is called denaturing. The substrate cannot fit, so cannot react so quickly.
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